Press for hydrostatic extrusion of long billets

ABSTRACT

A press for the hydrostatic extrusion of long billets has a stand with a pressure generating chamber and a pressure generating plunger insertable in the pressure generating chamber to generate high pressure in a pressure medium contained therein. A pressure chamber is arranged in line and communicates with the pressure generating chamber. A stationary support table is provided to take up axial forces on a die, and is spaced from the opening of the pressure chamber so that a die can be inserted into alignment with the opening of the pressure chamber. The support table contains a piston which is movable in the direction of the pressure chamber and on which the die support is carried for movement of the die into the opening of the pressure chamber opening.

United States Patent Nilsson et al.

[ July 24, 1973 PRESS FOR HYDROSTATIC EXTRUSION OF LONG BILLETS Averill et al. 72/60 Huddleston 72/60 Birman 72/60 Primary ExaminerRichard J. Herbst Attorney-Jennings Bailey, Jr.

[57] ABSTRACT A press for the hydrostatic extrusion of long billets has a stand with a pressure generating chamber and a pressure generating plunger insertable in the pressure generating chamber to generate high pressure in a pressure medium contained therein. A pressure chamber is arranged in line and communicates with the pressure generating chamber. A stationary support table is provided to take up axial forces on a die, and is spaced from the opening of the pressure chamber so that a die can be inserted into alignment with the opening of the pressure chamber. The support table contains a piston which is movable in the direction of the pressure chamber and on which the die support is carried for movement of the die into the opening of the pressure chamber opening.

7 Claims, 4 Drawing Figures PATENTEDJULZMQH SHEET 1 BF 2 PATENTED 3. 747. 383

sum 2 OF 2 PRESS FOR HYDROSTATIC EXTRUSION OF LONG BILLETS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press for hydrostatic extrusion of long billets.

2. The Prior Art In a hydrostatic extrusion process a billet is inserted in a pressure chamber and compressed by means of an all-sided hydrostatic pressure so that it is forced out through an opening in a die which gives the product the desired cross-section. Extremely high pressures are usually used, in the region of -20 kbar, preferably -20 kbar. The pressure is generally generated by forcing a plunger into a pressure chamber filled with liquid, the plunger being operated by'means of a hydraulic operating piston. The usuable pressure volume is determined by the length of the pressure-generating piston and the diameter of the pressure chamber. The buckling strength of the pressure-generating plunger limits this length.

When hydrostatically extruding material having great deformation resistance, for example steel, it is only possible to achieve an extrusion ratio of 3 8 depending on the hardness, with a pressure of 15 kbar. When the billet is placed in the pressure chamber where the pressure-generating plunger generates the pressure, a low production rate is obtained for steel of slim dimensions since the volume of the starting billet must be small in view of the slight extrusion ratio. In order to increase the capacity per operating cycle, a pressure-generating chamber may be used which has an inner diameter suitably chosen with respect to the strength of the walls of the pressure chamber and the buckling strength of the pressure-generating plunger, so that the greatest possible usuable volume is obtained under given circumstances such as available press stand and available driving power. This pressure-generating chamber is connected to a separate extrusion chamber where the billet and the die are placed. If pressure above about 7 kbar are to be used, it is necessary to place the pressure chamber in line with the pressure-generating chamber so that a durable connection can be obtained between the chambers. When steel is being extruded with an extrusion ratio of 3 8 the length of the pressure chamber may be considerable. Lengths of 5 to 15 metres are possible. Presses of this type are particularly suitable for manufacturing sections with cross-sections which are difficult to roll, for example triangular crosssection. In order to fill the pressure chamber as well as possible, it is preferable to start with a circular rod. In order to increase the extrusion ratio, extrusion and drawing may be carried out simultaneously.

SUMMARY OF THE INVENTION The press according to the invention has a pressuregencrating chamber and an extrusion chamber arranged in line with it. At the end of the extrustion chamber facing away from the pressure-generating chamber there is a press table which takes up the force operating on the die during the extrusion process. The support table is preferably joined to the stand of the pressure-generating chamber by a number of connecting rods, but it may also be anchored in a base of sufficient stability. Between the support table and the pressure chamber is an opening which makes it possible to insert a die from the side to a position opposite the press chamber opening and then into the pressure chamber, after which a die support is inserted in the opening. This, either directly or through other elements transmits the force operating on the die to the support table. The die support may comprise a support block which is inserted from the side between the pressure chamber and the support table and rests directly on the support table. The die support may also be carried by one or more pistons or consist of a piston running in a cylinder in the support table. The piston may be displaced towards the pressure chamber and locked in relation to the stationary support table or be influenced during the entire extrusion process by a pressure medium having such high pressure that the force of the piston with all certainty exceeds the force of the die operating in the opposite direction. In the latter case gaps can be eliminated between the various construction elements when the connecting rods are strained. In this way, reliable sealing elements can be used and the connecting rods need not be over-dimensioned to limit the displacement of the stationary support table due to the load. A piston arranged in line with the pressure chamber must of course have a bore for the product being extruded and must therefore be in the form of a differential piston or ring piston.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further described with reference to the accompanying drawings:

FIG. 1 shows schematically a press according to the invention;

FIG. 2 shows the support table with a die holder in the form of a differential piston;

FIG. 3 the connection between the pressuregenerating chamber and the extrusion chamber; and

FIG. 4 the side of the pressure-generating chamber facing the operating cylinder of the press.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, 1 designates a stand comprising two yokes 2 which are held together by a pre-stressed strip mantle 3. In this stand is an operating cylinder 4 having a differential piston 5 which carries a pressuregenerating plunger 6. In the stand is also a pressure chamber 7 which is formed by a cylinder 8, plunger 6 and cylinder 9. In order to generate a pressure in the pressure medium, usually castor oil, in the pressure chamber 7, the plunger 6 is moved into the chamber 7 by supplying a pressure medium through a conduit 11 which is in communication with a pressure medium source, not shown. The plunger 6 is returned by supplying pressure medium through the channel 13 to the chamber 12. In line with an opposite to the pressure chamber 7 is an extrusion chamber 14 which is formed by the tube 15, connection tube 16 and a die 17 which is inserted into the tube 15 during the extrusion process.

In the press is a support table 18 which takes up the force exerted on the die 17 during the extursion process. The support table 18 is joined to the yoke 2 of the stand by a number of connecting rods 19. An operating cylinder 20 (FIG. 2) is arranged in the support table 18, in which there is an axially movable piston 21 carrying a die support 39. The piston 21 is shaped as a differential piston with a head part 21a and a tube 21b joined to the head part. Both parts are provided with bores 22, 23 and 24 to provide a passage through the piston for the extruded product. The die support 39 is clamped against the piston part 21a by means of ring elements 25 and 26. Between the cylinder 20 and the piston 21a, 21b are seals 27 and 28 which are kept in place by elements 29 and 30, 31 and 32, respectively. The piston parts 21a and 2ab are joined together by the ring 33 and bolts, not shown. The piston 21a, 21b is moved towards the tube 15 by supplying pressure medium to the chamber 34 through a channel 35 which is in communication with a source of pressure medium, not shown, by means of conduits and valves, not shown. The piston is returned with the help of operating cylinders, not shown.

The pressure chamber 14 (FIG. 3) communicates with the pressure-generating chamber 7 through holes 40 and 41 in the tube 16 and cylinder 9, respectively. Between the cylinders 9 and 8 is a seal 42. The gaps 43 and 44 between the cylinder 9 and the tube 16 and between the tube 16 and the tube 15, respectively, forming parts of the extrusion chamber 14, are bridged by expanding sealing rings 47 provided with O-rings 45 and 46.

The tube 15 which constitutes an element of the extrusion chamber 14 is generally arranged stationarily in the press. A billet to be extruded is inserted in the chamber through the holes 22, 23, 24 in the die support 39 and the piston 21a, 21b, after which a die is placed opposite the opening of the tube 15 and the piston '21 is moved towards the tube 15 and pushes the die into the tube, keeping it in position during the extrusion process. In order to obtain sealing abutment between the point of the billet and the die 17 a billet holder may be used prior to the start of the extrusion process, of the type described in U.S. Pat. No. 3,531,965 or a spring inserted in the tube which rests against a support in the connecting tube 16. It is also possible to use two tubes 15 and insert a billet and a die in one of the tubes while this is outside the press and 1 the other tube is inside the press. The tube can thus be provided with a new billet while extrusion is in progress.

For the filling and ventilation of the pressuregenerating chamber 7 andthe extrusion chamber 9, the lefthand part of the pressure-generating chamber may be designed as shown in FIG. 4. At the end where the pressure-generating plunger 6 projects into the pressure chamber 7 there may be an end piece 50. In the end piece is a seal 41 which seals between the end piece and the pressure-generating plunger. Between the end piece 50 and the tube 8 is a high pressure seal 52 which seals between the tube 8 and the plunger 6 when the plunger 6 is pushed into the pressure chamber 7 and generates the pressure necessary for the extrusion process. There are also two channels 53 and 54 in the end piece, which open out between the seals 51 and 52. The

pressure chamber 7 is filled before the extrusion process with a pressure medium from a source, not shown, which is in communication with the channel 53 by a conduit and valves, not shown. The channel 54 permits escape of air of the pressure chamber during filling. It is connected to a drainage conduit which may have a valve which is closed when the air has been pressed out of the pressure chamber and this chamber is therefore filled with a liquid pressure medium. The pressure can then be considerably increased even before the pressure-generating piston is inserted. Pressures of between 25 500 bar are feasible. In the U. S. application Ser. No. 118,682, filed Feb. 25, 1971, Nilsson et al, now U.S. Pat. No. 3,702,555 suitable hydraulic systems are shown for filling the pressure chamber in the manner indicated.

We claim:

1. Press for hydrostatic extrusion of long billets comprising a press stand having spaced yokes, a first pres sure generating chamber and an operating cylinder with a pressure generating plunger to generate a high pressure in a pressure medium contained in the first pressure generating chamber, said first pressure generating chamber and said operating cylinder being arranged between said yokes in said press stand, a second pressure chamber communicating with the first pres sure generating chamber and arranged outside said press stand and in line with the first pressure generating chamber, a stationary die support connected to said press stand, said second pressure chamber being positioned between one yoke of said press stand and said stationary die support table, said table taking up axial forces exerted on the die, the second pressure chamber and the support table being spaced apart to provide an opening therebetween, and a die insertable into said opening.

2. Press according to claim 1 having connecting members joining the support table to said press stand.

3. Press according to claim 2, in which a yoke in said press stand, the connecting members and the die support table form a second press stand.

4. Press according to claim 3, in which a die support member is displaceable with respect to the support table and the second pressure chamber towards and away from said second pressure chamber.

5. Press according to claim 1, in which an operating cylinder is arranged in the support table and the support member is a piston arranged in said cylinder.

6. Press according to claim 5, in which the piston is a differential piston and has a passage therethrough which permits the passage of an extruded product through the piston.

7. Press according to claim 5, in which the piston is a differential piston and has a passage thercthrough which permits the passage ofa billet through the piston. i 

1. Press for hydrostatic extrusion of long billets comprising a press stand havIng spaced yokes, a first pressure generating chamber and an operating cylinder with a pressure generating plunger to generate a high pressure in a pressure medium contained in the first pressure generating chamber, said first pressure generating chamber and said operating cylinder being arranged between said yokes in said press stand, a second pressure chamber communicating with the first pressure generating chamber and arranged outside said press stand and in line with the first pressure generating chamber, a stationary die support connected to said press stand, said second pressure chamber being positioned between one yoke of said press stand and said stationary die support table, said table taking up axial forces exerted on the die, the second pressure chamber and the support table being spaced apart to provide an opening therebetween, and a die insertable into said opening.
 2. Press according to claim 1 having connecting members joining the support table to said press stand.
 3. Press according to claim 2, in which a yoke in said press stand, the connecting members and the die support table form a second press stand.
 4. Press according to claim 3, in which a die support member is displaceable with respect to the support table and the second pressure chamber towards and away from said second pressure chamber.
 5. Press according to claim 1, in which an operating cylinder is arranged in the support table and the support member is a piston arranged in said cylinder.
 6. Press according to claim 5, in which the piston is a differential piston and has a passage therethrough which permits the passage of an extruded product through the piston.
 7. Press according to claim 5, in which the piston is a differential piston and has a passage therethrough which permits the passage of a billet through the piston. 